NEC Article 220

Residential Load Calculation

The NEC 220.82 optional method (standard for single-family dwellings), the NEC 220 Part III standard method, continuous vs non-continuous loads, the 125% rule, and a full worked example for a 2,000 sq ft all-electric home with an EV charger.

By Brian WilliamsPublished April 21, 2026Updated April 22, 2026

Quick answer: For single-family dwellings, use the NEC 220.82 optional method. Add general lighting (3 VA/sq ft), two small-appliance circuits (1,500 VA each), laundry (1,500 VA), nameplate VA of all fixed appliances, and the largest of heat or cool. Apply 100% to the first 10 kVA, 40% to the remainder. Divide by 240V to get service amps.

Optional vs Standard Method

NEC 220.82 Optional Method

• For single-family dwellings only
• Simpler: one demand factor table
• First 10 kVA at 100%, remainder at 40%
• Plus largest of heating or cooling at 100% (or 65% for heat pump with backup)
• Used for 95% of residential load calcs

NEC 220 Part III Standard Method

• Required when optional does not apply
• Multiple demand factor tables by load type
• General lighting: 3 VA/sq ft, first 3 kVA at 100%, 3 to 120 kVA at 35%
• Range demand per Table 220.55
• Dryer demand per Table 220.54
• Yields a more conservative (larger) number than optional

The Core Inputs (NEC 220.82)

General lighting load

NEC 220.12

3 VA per square foot of habitable dwelling area. Counts lighting and general-purpose receptacles.

Small appliance branch circuits

NEC 210.11(C)(1)

At least two required in the kitchen and dining area. Count 1,500 VA each in the load calc, for a minimum of 3,000 VA.

Laundry branch circuit

NEC 210.11(C)(2)

One required, 1,500 VA in the load calc. Must not serve any other load.

Fixed appliances nameplate

NEC 220.82(B)(3)

Dishwasher, disposal, microwave, water heater, dryer, range, pool pump, hot tub, EV charger. Use nameplate VA or the 2019 NEC default values where nameplate is unknown.

Largest of heating or cooling

NEC 220.82(C)

Compare the heating load (furnace blower for gas, or full electric heating load) and cooling load (AC condenser + air handler). Use only the larger. For heat pumps with electric backup, include 65% of the backup resistance load.

Continuous loads at 125%

NEC 210.19, 215.2

At the branch circuit and feeder level, continuous loads (operating 3+ hours) are sized at 125%. This affects breaker and wire size, but for the service load calc itself, use nameplate VA for the service-level sum.

Worked Example

Scenario: 2,000 sq ft home in suburban New Jersey. Electric range, electric dryer, electric water heater, central AC (3 ton), gas heat (no electric resistance), planned 48A EV charger addition. Calculate service size under NEC 220.82.

Step 1: List all loads

Appliance	Nameplate VA	Demand Factor Bucket	Contributed VA
General lighting (2,000 sq ft)	2,000 x 3 VA = 6,000 VA	100% first 10 kVA	6,000 VA
Small appliance (2 circuits required)	1,500 VA x 2 = 3,000 VA	100% first 10 kVA	3,000 VA
Laundry circuit	1,500 VA	100% first 10 kVA	1,500 VA
Dishwasher	1,200 VA	other loads	1,200 VA
Disposal	600 VA	other loads	600 VA
Microwave	1,500 VA	other loads	1,500 VA
Electric range (8 kW)	8,000 VA	other loads	8,000 VA
Electric dryer	5,500 VA	other loads	5,500 VA
Water heater (4.5 kW)	4,500 VA	other loads	4,500 VA
EV charger (48A x 240V)	11,520 VA	other loads (continuous)	11,520 VA
AC condenser (3 ton)	4,500 VA	largest of heat or cool	4,500 VA

Step 2: Sum general + appliance loads (before demand factor)

General lighting (2,000 x 3 VA): 6,000 VA
Small appliance circuits (2 x 1,500 VA): 3,000 VA
Laundry: 1,500 VA
Dishwasher: 1,200 VA
Disposal: 600 VA
Microwave: 1,500 VA
Electric range: 8,000 VA
Electric dryer: 5,500 VA
Water heater: 4,500 VA
EV charger: 11,520 VA
Subtotal: 43,320 VA

Step 3: Apply 220.82 demand factor

First 10,000 VA at 100%: 10,000 VA
Remainder (43,320 - 10,000 = 33,320 VA) at 40%: 13,328 VA
Subtotal after demand: 23,328 VA

Step 4: Add largest of heat or cool

Heating (gas furnace blower only): ~800 VA
Cooling (3-ton AC): 4,500 VA
Use larger of the two: 4,500 VA
Running total: 27,828 VA

Step 5: Convert to amps at 240V

Total VA / 240V = Service amps

27,828 VA / 240V = 115.95A

Result: a 150A service would work, but given typical good-practice margin and the possibility of adding a second EV or a heat pump later, most electricians would recommend a 200A service here. A 100A service fails this calc.

Continuous Load and the 125% Rule

Separate from the service load calc, any branch circuit or feeder that serves a continuous load must be sized at 125% of that continuous load plus 100% of any non-continuous load on the same circuit.

EV charger

Continuous; 125% rule applies to the branch breaker and wire. 48A EVSE requires 60A breaker and 6 AWG copper.

Electric water heater

Usually non-continuous (resistance element cycles on thermostat); sized per nameplate. Heat pump water heaters sometimes treated as continuous.

Baseboard heat / electric furnace

Continuous during heating season; 125% on branch and feeder.

Air conditioning

Non-continuous per NEC definition (operates less than 3 hr continuously in cycles); sized per 440 for HVAC.

Range, dryer, dishwasher, disposal

Non-continuous; sized per nameplate with range and dryer demand tables in standard method.

Dwelling lighting (general)

Typically treated as non-continuous for dwellings; commercial lighting is continuous.

When to Upgrade Based on the Calc

Calc at 100% or more of service

Upgrade required. Inspectors will not pass a load calc showing 205A on a 200A service.

Calc at 80 to 99% of service

Technically compliant, but most electricians recommend upsize, particularly if future electrification (EV, heat pump) is planned.

Calc at 60 to 79% of service

Good margin. Adding a single EV charger, heat pump, or minor appliance is typically fine without upgrading.

Calc under 60% of service

Significant headroom. Service is oversized for current usage; focus on adding circuits and efficiency upgrades, not service changes.

Frequently Asked Questions

Do I need to do a load calc for every permit?

Most jurisdictions require a load calculation only for service-related work: new services, panel upgrades, service changes, or additions that include large loads (EV charger, heat pump, pool heater, hot tub, induction range). Simple circuit additions rarely require a full calc. That said, electricians routinely do informal load calcs for any project adding over 20A of new load, because the AHJ can demand one at inspection.

What do inspectors actually check on a load calc?

Inspectors look for: (1) correct square footage and 3 VA/sq ft for general lighting, (2) the two mandatory 1,500 VA small-appliance circuits, (3) the 1,500 VA laundry circuit, (4) all fixed appliances listed with nameplate VA or the code-allowed value, (5) correct demand factors applied (first 10 kVA at 100%, remainder at 40% under 220.82), (6) heat vs cool compared and the larger one used, (7) final amperage compared to service rating. A calc showing 205A on a 200A service is a fail.

What is the difference between continuous and non-continuous loads?

A continuous load operates for 3 hours or more at maximum current: EV chargers, electric heat, lighting, large motors. Non-continuous loads cycle on and off: ranges, dryers, dishwashers, microwaves. NEC 210.19 and 215.2 require branch circuits and feeders to be sized at 125% of the continuous load plus 100% of the non-continuous load. Most load calc spreadsheets handle this automatically, but it is the most-missed factor on hand calcs.

When does the 125% rule apply?

The 125% continuous-load factor applies to the branch circuit or feeder that supplies the continuous load, not to the load entry in the overall service calc. Example: an EV charger entered as 48A continuous would require a 60A branch breaker (48 x 1.25 = 60), but in the NEC 220.82 optional service calc, it contributes its nameplate kVA to the "other loads" bucket. The branch-level 125% and the service-level demand factor are separate calculations.

How does a heat pump vs gas furnace affect the load calc?

Heat pumps are fully electric, so the heating load (typically 5 to 15 kW for a whole-house system) enters the calc and competes with cooling for the "largest of heat or cool" entry under 220.82(C). A gas furnace contributes only its blower motor (typically 0.5 to 1 kW) and pulls HVAC load mostly into the cooling side. Switching from gas to a heat pump often adds 15,000 to 30,000 VA to the load calc, which is why heat pump retrofits sometimes force a 200A service upgrade.

When do I use optional vs standard method?

Use the NEC 220.82 optional method for single-family dwellings with standard loads; it is simpler and almost always yields a smaller (more permissive) result. Use NEC 220 Part III standard method when you have unusual loads not covered by the optional method, multiple dwelling units, or when the AHJ specifically requires it. Most residential electricians default to optional for 99% of jobs and only use standard when optional does not apply.

How do I calculate a subpanel feeder load?

Sum the loads on the subpanel the same way as a service: general lighting at 3 VA/sq ft for the area served, small appliance circuits if fed by the subpanel, fixed appliances, plus any large continuous loads at 125%. Apply demand factors from 220.84 (for multi-family feeders) or 220.82 (for single-family). The feeder ampacity is the larger of the calculated load or the subpanel main breaker rating.

What if my calc is wrong after install?

If the actual load exceeds the calc and the breaker trips or the service equipment overheats, you have a few options: (1) shed load by switching gas appliances back or installing load management, (2) upsize the service (panel upgrade), (3) add a subpanel with automatic load control for the EV or HVAC. Submitting an updated load calc and pulling a revision permit is the right path; ignoring the problem risks insurance denial on a fire claim.